主控提前点火对复合推进剂慢速烤燃响应的影响

Effect of pre-ignition on slow cook-off response characteristics of composite propellant

为研究主控点火对复合推进剂慢速烤燃响应特性的影响,设计并开展了典型复合推进剂装药慢速烤燃实验,结合数值计算和推进剂热分解失重及形貌演化过程,探讨了点火前推进剂内的温度分布情况及推进剂细观结构热损伤规律。研究发现:针对复合推进剂装药的慢速烤燃,在推进剂发生自热点火前温度较低时进行主控点火可以有效降低反应剧烈程度;随着加热温度的升高,推进剂中部分组分发生分解,导致推进剂内部温度高于壳体温度,同时推进剂中粘结剂及AP的分解会导致推进剂装药形成多孔状的结构,在点火后更易导致对流燃烧,加剧反应烈度;当壳体温度仅138℃时,推进剂温度最高点达到150℃,最高点首先出现在靠近喷管的尾部,考虑到粘结剂及AP部分分解导致的孔隙结构会加剧反应的响应烈度,主控点火温度应设定在138℃以下。

The study of slow cook-off of composite propellant containing ammonium perchlorate(AP)is the focus of the research on propellant safety,while the pre-ignition is a common and effective way to reduce the intensity of reaction in slow cook-off of engine.To investigate the effect of pre-ignition temperature on its response characteristics,a set of slow cook off experiments of composite propellant was designed and carried out,and the response characteristics of ignition at different temperatures were studied.The temperature distribution of the propellant and the thermal damage law of propellant microstructure before ignition were investigated by numerical simulation and thermal decomposition experiment.The results show that the engine spontaneously ignited with a reaction level of violent explosion,and the reaction level was burning when it was ignited at 120℃.The intensity of the reaction could be reduced effectively by pre-ignition when the propellant temperature was low before auto-ignition.The thermal decomposition process and thermal structure damage evolution of the propellant during slow cook-off were studied by thermogravimetry analysis combined with morphological characterization.As the heating temperature increased,some components of the propellant were decomposed,causing the internal temperature of the propellant to be higher than that of the shell,while the breakdown of binders and AP in the propellant resulted in a porous structure of the propellant charge,more likely leading to convection combustion after ignition and increasing the intensity of the reaction.Due to the autothermal reaction of the propellant,the highest temperature of the propellant reached 150℃when the shell temperature was only 138℃.The highest temperature first appeared near the tail of the nozzle.Considering the influence of porous structure caused by AP decomposition on the intensity of reaction,the ignition temperature in advance should be lower than 138℃.In order to avoid the decomposition in the propellant to produce porous structure,which would cause severe reaction after ignition,some measures should be taken in igniting the propellant before the main propellant reaches auto-ignition temperature,which can effectively reduce the intensity of reaction.